Argon condensation system and method

Patent metadata

Field	Value
Publication number	US-10247471-B2
Application number	US-201816032204-A
Country	US
Kind code	B2
Filing date	Jul 11, 2018
Priority date	Jul 2, 2014
Publication date	Apr 2, 2019
Grant date	Apr 2, 2019

Abstract

An argon reflux condensation system and method in which a plurality of once-through condensers are connected to an argon column of an air separation plant to condense argon-rich vapor streams for production of reflux to the argon column. Condensation of the argon-rich vapor streams is brought about through indirect heat exchange with crude liquid oxygen streams that partially vaporize and are introduced into a lower pressure column of the plant for further refinement. The flow rate of the crude liquid oxygen streams are sensed and controlled at locations in the air separation plant where the crude liquid oxygen is in a liquid state and in proportion to the size of the once-through heat exchangers. Prior to flowing into the once-through condensers, the partially vaporized crude oxygen stream enters a phase separator which separates the crude oxygen vapor from the crude liquid oxygen. The separated crude oxygen vapor bypasses the once-through condensers and is mixed with the vaporized oxygen stream that exits the one-through condensers. Feed stream flow rate to the argon column is controlled in response to air flow rate to the plant and product flow rate is controlled in response to the feed stream flow rate to the argon column.

First claim

What is claimed is:

1. A method of condensing argon reflux within an air separation unit having an argon column, a lower pressure column and a higher pressure column, said method comprising the steps of:
extracting a crude argon feed stream from the lower pressure column;
distilling the crude argon feed stream in the argon column to produce an argon-rich vapor column overhead;
directing at least a portion of the argon-rich vapor column overhead to a plurality of once-through heat exchangers;
condensing the argon-rich vapor streams within condensation passages of the plurality of once-through heat exchangers such that argon-rich vapor streams composed of argon-rich vapor column overhead are condensed within condensation passages of the once-through heat exchangers to produce an argon-rich liquid product stream and argon-rich liquid reflux stream
returning the argon-rich liquid reflux stream to the argon column as reflux;
partially vaporizing a stream of crude liquid oxygen column bottoms from the higher pressure column to form a partially vaporized crude oxygen feed stream;
separating the partially vaporized crude oxygen feed stream in a phase separator into at least one crude oxygen vapor stream and at least one crude liquid oxygen stream;
introducing the at least one crude liquid oxygen stream into vaporization passages of the plurality of once-through heat exchangers to partially vaporize the crude liquid oxygen streams through indirect heat exchange with the argon-rich vapor streams to produce partially vaporized crude oxygen streams;
directing the at least one crude oxygen vapor stream from the phase separator and the partially vaporized crude oxygen streams from the vaporization passages of the plurality of once-through heat exchangers into the lower pressure column;
sensing flow rates of the crude liquid oxygen column bottoms stream taken from the higher pressure column;
controlling the flow rates of the crude liquid oxygen bottoms stream taken from the higher pressure column in response to the sensed flow rates and the level of the crude liquid oxygen bottoms in the higher pressure column; and
controlling a feed stream flow rate of the crude argon feed stream in response to an air flow rate into the air separation unit and by controlling the reflux flow rate of the argon-rich liquid reflux by:
(i) decreasing the reflux flow rate of the argon-rich liquid reflux stream when the feed stream flow rate is above a feed stream set point to thereby cause the argon-rich liquid reflux to back up into the condensation passages of the once-through heat exchanger causing an increase in pressure of the argon-rich vapor stream and within the argon column; and
(ii) increasing the reflux flow rate of the argon-rich liquid reflux stream when the feed stream flow rate is below a feed stream set point to thereby cause a decrease in the pressure of the argon-rich vapor stream and within the argon column.

2. The method of claim 1 further comprising the step of controlling a product flow rate of the argon-rich liquid product stream in response to the feed stream flow rate of the crude argon feed stream.

3. The method of claim 1 wherein the step of controlling the flow rates of the crude liquid oxygen bottoms streams further comprises:
controlling the flow rates of the crude liquid oxygen bottoms stream taken from the higher pressure column to the plurality of once-through heat exchangers via one or more flow control valves; and
adjusting the flow control valves to attain a flow rate set points that are based on the sensed flow rates and the level of the crude liquid oxygen bottoms in the higher pressure column;
wherein the flow rate set points are decreased as the level of the crude liquid oxygen bottoms in the higher pressure column decreases and the flow rate set points are increased as the level of the crude liquid oxygen bottoms in the higher pressure column increase.

4. The method of claim 2 wherein the feed stream set point is a function of the air flow rate into the air separation unit multiplied by a crude fraction.

5. The method of claim 2 further comprising the steps of:
measuring temperatures of the partially vaporized crude oxygen feed stream; and
further controlling the feed stream flow rate of the crude argon feed stream and the argon-rich liquid product stream product flow rate in response to the measured temperatures of the a partially vaporized crude oxygen feed stream,
wherein the feed stream flow rate of the crude argon feed stream decreases when the temperatures of the partially vaporized crude oxygen feed stream is above a predetermined temperature indicative of dry out conditions within the vaporization passages.

6. The method of claim 2 further comprising the steps of:
measuring temperatures of the partially vaporized crude oxygen feed stream; and
controlling the reflux flow rate of the argon reflux stream in response to the measured temperatures of the partially vaporized crude oxygen feed stream;
wherein the reflux flow rate of the argon reflux stream is decreased causing the argon-rich liquid to back up into the condensation passages and further causing an increase in pressure of the argon-rich vapor stream and within the argon column when the temperatures of the partially vaporized crude oxygen feed stream is above a predetermined temperature indicative of dry out conditions within the vaporization passages.

7. The method of claim 2 further comprising the steps of:
measuring the flow rate of the argon-rich liquid product stream;
further controlling the flow rate of the argon-rich liquid product stream via one or more product flow control valves to maintain the flow rate of the argon-rich liquid product stream at a product flow rate set point;
wherein the product flow rate set point being a function of the feed stream flow rate of the crude argon feed stream multiplied by a product fraction.

8. The method of claim 1 wherein the liquid level in the phase separator is maintained at a prescribed level to provide the liquid head required to drive flow of the crude liquid oxygen stream through the plurality of once-through heat exchangers.

9. The method of claim 1 wherein the pressure in the phase separator is maintained at a prescribed level required to drive flow of the crude liquid oxygen stream through the plurality of once-through heat exchangers.

10. The method of claim 1 wherein the liquid level in the phase separator and the pressure in the phase separator are maintained at prescribed levels to drive flow of the crude liquid oxygen stream through the plurality of once-through heat exchangers.

11. The method of claim 1 wherein the flow rate of the crude liquid oxygen column bottoms from the higher pressure column are controlled such that the one or more partially vaporized crude liquid oxygen streams exiting the vaporization passages of the plurality of once-through heat exchangers each comprise about 10% or more of the crude liquid oxygen stream so as to prevent dry-out within the vaporization passages of the plurality of once-through heat exchangers.

12. The method of claim 1 wherein the liquid flow rates of the crude liquid oxygen column bottoms from the higher pressure column are controlled such that the one or more partially vaporized crude liquid oxygen streams exiting the vaporization passages of the plurality of once-through heat exchangers collectively comprise about 20% or more of the crude liquid oxygen stream so as to prevent dry-out within the vaporization passages of the once-through heat exchangers.

Assignees

• Handley James R
• Powell Brian S
• Howard Henry E
• Chakravarthy Vijayaraghavan S
• Shelat Maulik R
• Falta Steven R
• Praxair Technology Inc

Inventors

• Handley James R
• Powell Brian S
• Howard Henry E
• Chakravarthy Vijayaraghavan S
• Shelat Maulik R
• Falta Steven R

Classifications

• F25J3/048 Primary

  Argon recovery · CPC title

• F25J2250/20

  Boiler-condenser with multiple exchanger cores in parallel or with multiple re-boiling or condensing streams · CPC title

• F25J3/04715

  The auxiliary column system simultaneously produces oxygen · CPC title

• F25J2250/02

  Bath type boiler-condenser using thermo-siphon effect, e.g. with natural or forced circulation or pool boiling, i.e. core-in-kettle heat exchanger · CPC title

• F25J3/04678

  cooled by oxygen enriched liquid from high pressure column bottoms · CPC title